Fluke 45 Frequency Measurement Rates, Frequency Sensitivity Selection, Measuring Frequency

Operating the Meter From the Front Panel	3
Measuring Frequency

Frequency Measurement Rates

The rate at which frequency measurements are taken is a factor of the frequency being measured (see Table 3-6).

When the frequency function has been selected, pressing Rhas no effect on the frequency update rate.

Table 3-6. Frequency Measurement Rates

Frequency

@> 150 Hz

@100 Hz

@60 Hz

@15 Hz

@10Hz

@5Hz

Reading Rate

1.8/sec

1.6/sec

1.3/sec

1/1.2sec

1/1.7sec

1/3.2 sec

Measuring Frequency of Current (100 mA and 10A) Inputs

Frequency measurements are always taken using the ac input circuitry of the meter. Normally, measurements are taken on the Xinput terminal. However, frequency measurements can also be taken on current inputs. If frequency is to be measured using a current input, ac current must be selected in the primary display and frequency must be selected in the secondary display.

When the ac current function in a mA range is selected in the primary display and frequency is selected as the secondary display function, the frequency of the current at the 100 mA terminal will be measured. Similarly, when the ac current function in the 10 A range is selected for the primary display and frequency is selected in the secondary display, the frequency of the current at the 10 A input terminal is measured.

Frequency Sensitivity Selection

Before a frequency measurement is started, the amplitude of the input signal is sampled and the optimum ac range is selected automatically. For most applications, therefore, the user need not be concerned with setting the measurement sensitivity for stable frequency readings.

However, if necessary, measurement sensitivity can be selected manually. To do so, use the dual display as described in the following procedure:

1.Power-up the meter and press Zor Dto select an ac voltage or current function in the primary display.

2.Press E,U, or Tto manually select an ac measurement range.

3.Press Sthen press Fto select the frequency function in the secondary display.

All frequency measurements on the secondary display will be taken on the selected ac range.

The maximum input voltage that may be applied on any ac measurement range for reliable frequency measurements is listed in Table 3-7.

The minimum signal for a stable frequency measurement varies depending on the frequency and waveform being measured.

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